All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
An optical fiber characteristics measurement device, as is widely known, is a device that inputs continuous light or pulse light into an optical fiber, receives scattered light or reflected light that occurs within the optical fiber, and measures temperature distribution, strain distribution, and other characteristics in the longitudinal direction of the optical fiber. In this optical fiber characteristics measurement device, because the received scattered light or reflected light varies in response to physical quantities (for example, temperature and strain) that influence the optical fiber, the optical fiber itself is used as a sensor.
Patent Document 1 noted below discloses an optical fiber characteristics measurement device in which frequency-modulated continuous light (pump light and probe light) is sent into each respective end of the optical fiber, thereby forming periodic correlation peaks between the pump light and the probe light along the optical fiber, a characteristic of the optical fiber being measured by utilizing the property that the probe light is amplified by the stimulated Brillouin scattering only a positions of the correlation peaks. This optical fiber characteristics measurement device, by receiving amplified probe light at each position while varying the correlation peak positions within the optical fiber, can measure the characteristics of an optical fiber in the longitudinal direction.
Patent Document 2 discloses an optical fiber characteristics measurement device in which frequency-modulated continuous light (probe light) and pulse light (pump light) are sent into one and into the other end of an optical fiber, causing successive correlation peaks in accordance with the position of the pump light that propagates within the optical fiber, so as to obtain only light (stimulated Brillouin scattered light) in the vicinity of a measurement point of the light exiting from the optical fiber, so as to measure the characteristics of the optical fiber at the measurement point. This optical fiber characteristics measurement device adjusts the modulation frequency of the probe light and the pump light and the timing of receiving the light exiting from the optical fiber, so as to move the measurement point, thereby enabling measurement of the characteristics at an arbitrary position along the longitudinal direction of the optical fiber.